Green synthesis of silver nanoparticles using sodium alginate and tannic acid: characterization and anti-S. aureus activity

Multi-drug resistance and biofilm formation are a growing problem in the treatment of Staphylococcus aureus contamination. Advances in nanotechnology allow the synthesis of metal nanoparticles that can be assembled into complex architectures for controlling bacterial growth. This study aims to investigate the ultrasonic-assisted green synthesis of silver nanoparticles (AgNPs) by tannic acid (TA) and sodium alginate (Na-Alg) as the reducing and stabilizing agents, respectively, and evaluation of their antibacterial and antibiofilm activities. The UV-Vis spectroscopy and transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), zetasizer, FT-IR spectroscopy, and X-ray diffraction (XRD) studies showed that the optimum produces were spherical, stable, and monodispersed AgNPs with an average size of particle sizes of 18.52 ± 0.07 nm. The antibacterial and antibiofilm activities of the AgNPs loaded TA/Na-Alg constructs against S. aureus ATCC 6538 were investigated. The minimum inhibitory concentration (MIC) of the AgNPs was 31.25 μg/mL. After exposure to the AgNPs, planktonic S. aureus showed irreversible cell membrane damage, decreased cell viability, and changes in cellular morphology. In addition, the AgNps significantly inhibited S. aureus biofilm formation at 1/32 MIC. The biofilm elimination rate was 58.87% after exposure to MIC AgNPs. The results suggested that the development of AgNPs loaded TA/Na-Alg constructs with biomedical potentialities obtained through a simple, green, and cost-effective approach, may be suitable for the formulation of a new strategy for combating S. aureus.